What happened

Shares of Amarin Corporation plc (NASDAQ:AMRN), a cardiovascular health-focused biotech, popped 12.9% higher this morning after reporting second-quarter earnings. Investors cheered the record-breaking results early, but the stock's gain has settled to about 3.4% as of 11:35 a.m. EDT on Wednesday.

So what 

Amarin's future is tethered to success for Vascepa, a triglyceride-lowering fish-oil derivative that earned approval in 2012, and got off to a fairly slow start. It looks like patience is paying off for early investors, though, as second-quarter sales of the drug rose 37% over the same period last year, to $44.9 million.

Finger pointing to an upward sloping chart.

Image source: Getty Images.

The latest quarter was the company's most successful yet, but Amarin isn't entirely out of the woods just yet. Although the company is steadily approaching profitability, it still reported an $11.4 million operating loss during the second quarter.

Now what

Amarin stock will probably continue to jump around until investors are certain the company can cross the profitability threshold before burning through its cash reserves, which stood at about $85.5 million at the end of June. Today's full-year product-revenue-expectation upgrade, which moved the range $10 million higher to between $165 million and $175 million, is a step in the right direction. 

One factor helping Vascepa sales reach the recently inflated goal is a positive readout from a clinical trial testing the drug's ability to lower triglycerides for diabetic women who aren't responding strongly enough to statin treatment. Further ahead, though, lies the company's most important readout.

Although Amarin's drug clearly reduces triglycerides, evidence that it provides a long-term mortality benefit would make its sales force's job much easier. The 8,175 patient Reduce-It study aims to prove or disprove such a benefit. The outcome trial, which began in 2011, is nearing completion. If the results, expected around the middle of next year are highly positive, the stock would enjoy a sustained lift.

Cory Renauer has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.